You don't really expect to see yourself in the emergency room the day before prom! We were heading to Hong Kong the morning after, and my father wanted us all to update our vaccinations because of the measles outbreak in the region we were heading to. I got to the doctor's office, received the shot, and got up and left the room right after because my mom wanted the doc to look at something on her leg.
Next thing I knew, I was on the ground and my glasses had shattered, carving a nice bloody pattern into the side of my head. Apparently I had gotten up after this, knocked on the door, said 'I don't feel so good' and promptly passed out again. I remember waking up on the floor, with about six different doctors and nurses just staring at me on the floor. I got carted to the ER, and once everything was sorted out I had a minor concussion and a nice lightning-shaped scar on the side of my face for a memento.
My make-up artist had a great time trying to camouflage my bruise and still-fresh injury the day after. The scar has faded (unfortunately), but it's left me with a great story to tell. Funny thing is that I work in a setting where I see tons of people get their shots, and I'm still the only person I know who has fainted from getting a vaccination!